A word from Christie, the 'Turbo the Snail' costume creator:

My 6 year old son is wearing the costume we made out of left-over card board. We cut the shape and then used a LOT of glue to get it to curve around the shell. Then we painted and used Battery-operated LED lights on the back so he would light-up at night. I used rubber bands around the inside that hooked around his arms to stay on.